Improvement in drafting-scales



J. LYMAN. DRAFTING SCALE.

.No.187,.290. Patented Feb.13,1877

UNITED STATES PATENT OFFICE.

J OSIAH LYMAN, OF LENOX, MASSACHUSETTS.

IMPROVEMENT IN DRAFTlNG-SCALES.

Specii'ication forming part of Letters Patent No. 187,290, datedFebruary 13, 1877; application tiled March 30, 1876.

-all made on the beveled part of the plate,

thus allowing of four separate scales on each late' secondl in a frameor mountin for this plate, (connected 'with a sliding spring,) whichgives an inclination to its iiat surface of about thirty degrees, or alittle more, to the plane-of the drafting-board on which it rests--oneof the beveled edges thus nearly coin iding with the paper, while theother is inclined to it at an angle of sixty degrees, or oi' thirtydegrees to the perpendicular thereto; thirdly, in the peculiarity of theverniers, and their combination with their frame and spring, asdescribed in detail.

` To enable others skilled in the art to comprehend and use myinvention@ Will describe in detail its construction and applications.

Figure l shows in plan the scale-plate with its fixtures all complete,as in use; including the holdingsprings, main 'sliding spring, with itsattachment to the frame and to the arm ofthe trigonometer, orprotractor, or Tsquare, and the vernier, with its sliding frame anddouble springs.

Fig. 2 is a transverse section of the instrument, through one ot' thebeveled posts ofthe frame. It shows the form, thickness, width, andinclination of the scale-plate, with the socket or orifice for therounded tooth of the post fitted to it, as indicated. It also exhibitsat two points the sliding y spring, viz, at its attachment to the postand in the curve, with the trigonometer arm and a portion of thedraftingboard on which the' whole rests.

Fig. 3 is a transverse section through the center of one of theholding-springs, showing how the latter is attached to the base of theframe, and the manner of its holding in its normal position thescale-plate.

Fig. 4. is a transverse section through the center of the thumb-uut,thumb-plate, and

lip, showing the manner in which the frameshowing the tooth of theformer fitted into a corresponding socket or groove in the latter, toprevent it from slipping forward.

Fig. 7 is a view in plan of the vernier; and

Fig. S is a view in plan of the vernier-frame before being bent into itsproper form, as shown in Figs. 5 and 6, the dotted lines showing theoutline of the vernier in its relative position. lt also shows theconstruction of the lip before being bent up and fitted to theVernier-socket.

Fig. 9 is a longitudinal section (through the ends of the slidingspring) of the scale-frame including its base B and posts P P.

Fig. l0 is a longitudinal section of the thumb-nut, thumb-plate, andsliding spring.

The several parts of this instrument may be described as follows Thescaleplate, usually made of German silver, is ordinarily eithersix and ahalt` or -twelve and a half inches long, three-quarters ot' an inchwide, and about one-fourteenth of an inch thick. The two edges, asillustrated in Figs. 2, 3, 4, 5, and 6, are double beveled. Thegraduated marks are cut clean with a wedge-shaped tool, like that of theengraverfnarrow, but so deep that When placed in its normal position' onits frame, the needle-pointwill readily, with invariable certainty andwhile held plumb, follow any one of them entirely down to the paper,thus forming a circular dot instead of an elliptic one, as isunavoidable when in clined.

The frame consists ofaplate of German silver, half an inch wide andone-fourteenth of an inch thick, with posts attached at or near the endsat right angles, as shown in Fig. 9. The tops of the posts are beveledto an angle of 300 vwith the base B, as shown in section P, Fig. 2. Thelength of Vthe frame is identical with that of the scale plate. On thebeveled part of these posts is left a projecting tooth, madecylindrical'at the base and spherical at the top, being thus fitted tocorresponding orifices in the scaleplate, as clearly shown in Figs. l,2. Through the posts, very near the rear edge and even with the uppersurface of the base, are drilled orifices for receiving the two ends ofthe sliding spring S Sp, Figs. l, 2, and 9.

The sliding spring S Sp is made of German silver wire one-twentieth ofan inch in diameter, bent into the shape shown, soldered to the littleGerman-silver plate Th, into which is screwed the thumb-nut Th, Figs. l,4, Aand l0. The rear border of the plate is bent down so as to form alip, L, Fig. 4; and the side borders are bent in a similar manner, buteX tend no lower than the bottom of the spring, as seen in Fig. 10. Thisspring, by its lip, holds the scale-frame firmly in contact with thetrigonometer or T-arrn, yet at theA same time admits of 'a smooth,steady, sliding motion, with friction increased or diminished atpleasure by bending; thus securing constant parallelism between thelower or working edge ofthe scale and the adjacent edge of thetrigouometer or T-arm. The same spring is applicable to either the footor six-inch scale, butin the former case sockets for the ends of thespring are fastenedto the frame at requisite distances from its center.

The holding-springs, H Sp, H Sp, Figs. l and riveted to the frame-base,Fig. 3, while they allow the scale-plate to be freely and easily slideither into or out of its normal position, at the same time hold itfirmly in contact with the posts at the required angle. These are alsomade of German silver.

The Vernier consists of a Germ .an-silver plate, alittle more than aninchin length, about threequarters of an inch wide, and one-iiftieth ofan inch'thi'ck, Figs. 5,' 6, and 7. The graduations are double. The twozero-marks being exactly one inch apart, the readings of the two arealways identical, and are therefore checks on each other, so as to givethe mean reading with twice the certainty of one. This twofold readingalso enables the operator to read the scale with equal ease from left toright or right to left. And this is a very essential facility; for, inordinary reading, the zero-line of the Vernier constitutes one of thetermini of any given or required distance, and one of the zero or unitlines of the scale the other; and in dotting any given distance, theneedlepoint is applied to the latter, but never to the former.

On the under side of the vernier, about the twentieth of an inch fromits upper edge, a longitudinal groove is cut, half or two-thirds throughthe plate (seen in section in Fig. 6)

into which the corresponding tooth of the Vernier frame is fitted, soas, while admitting of lateral motion for sliding into or out ofposition the vernier, to secure it against forward motion.

The vernier-frame, ,as shown in Fig. 8, has the precise form given it bythe die before being bent. In Fig. 5 may be seen in section the form,after being bent, of those portions which lie directly under theVernier-springs; and in Fig. 6 the form through Yits central section isexhibited.

The peculiar shape ofthe Vernier-springs is shown in width in Fig. l, VS V S, and in section in Fig. 5, V S. They are attached, as there shown,to the vernierframe by means of rivets or small screws and thumb nuts.The action of these springs is threefold, viz: first, to hold with oneend the Vernier snugly to its frame; secondly, with the other end tohold the frame in contact with the scale-plate, giving sufcient frictionto allow of smooth, uniform, lateral motion; and thirdly, by pressingthe lower edge of the Vernier irmly against the beveled face of thescale-plate to hold. the frame from slipping backward while being slidlaterally in its normal motion.

The foregoing specification and illustrations clearly show that thescale-plate may beinstantly slipped out from its position and inverted;or, with its ends or sides reversed, replaced so as to bring' any one ofthe four scales into working position; and also that either a decimal orduodecimal Vernier suited thereto may be in the same moment slipped intoposition for use.

Thus constituted, it is believed that for convenience, accuracy, orexpedition this scale, for all classes of rectilinear drafting, standsunrivaled.

l claiml. The dat scaleplate, constructed as set forth; in whichscale-plate each of the two longitudinal edges is double beveled to adefinite angle, viz, of about sixty degrees, and in which the four facesproduced by such beveling have each the same inclination of about thirtydegrees to their adjacent and corresponding flat surfaces.

2. A frame or mounting for this scaleplate, as shown, consisting ofbase, posts, (beveled to the same angle as the bevels of the plate,) andsliding spring; the posts holding the plate in uniform inclination tothe paper, and the spring holding the whole in firm contact with thetrigonometer or T-arm.

3. The combination, as described, of double verniers (suited to theseveral scales) with their frame and tri-acting spring.

JDSIAH LYMAN. Witnesses:

F. W. BALDWIN, ALBERT J. LYMAN.

